1. Field of the Invention
The present invention relates to an optical ring network, and in particular to an optical ring network employing wavelength division multiplexing.
2. Description of the Related Art
Recently, it has been recognized that it is essential for all optical networks to be configured to deal with tremendous growth in data traffic. To this end, various solutions have been proposed for configuring optical networks. In addition, due to considerable efforts in developing various optical transmission systems and optical routing devices various products are available on the market. An optical ring network, which is based on Wavelength Division Multiplexing (WDM), is a network topology that is attracting considerable attention. This is due to its easy configuration, switching restoration, reduction of initial costs and so forth. Such optical ring networks have already been adopted by many countries in the world.
Such an optical ring network is configured to perform communication between nodes using a plurality of channels. Specifically, one or more channels that are needed for the communication connection between the nodes are allocated to a pair of nodes and bi-directional communication is carried out through the channels. However, such networks have serious drawbacks in its flexibility, in particular, in coping with data traffic bursts. In addition, they have a significant decrease in the total bandwidth performance in the network. These drawbacks are due to the optical ring network being configured to route communication through channels and because these channels are set in advance.
To overcome these disadvantages, engineers have made significant progress in researching and developing an optical router which is based on optical packet switching (OPS) and optical burst switching (OBS). Nevertheless, many problems remain in realizing the OPS and OBS techniques. Since the OPS or OBS performs switching of packets or bursts, the packets or bursts should not only be free from collision with each other at each node in the network, but also should enable switching at a very fast speed. To solve the latter problems, (the problems caused by optical components such as optical buffers), high speed optical switches and so forth should be resolved first. For this reason, alternative solutions are being sought, which make use of a burst delay line, a wavelength converter, etc., all of which are based on optical fibers. However, such solutions have not yielded satisfactory results. Moreover, these solutions do not yet satisfy economic considerations, which generally take considerable time.
In short, conventional optical ring networks, which employ WDM and wherein optical paths are set by the channels, is suitable for transmission of high capacity static data, but not for transmission of burst data. Moreover, conventional networks make it impossible to effectively make use of a high capacity bandwidth without waste. Further, in the proposed optical router networks based on OPS and OBS, to compensate for the aforementioned drawbacks, components such as an optical buffer, a wavelength converter, etc. are absolutely needed to reduce collision between data. However, the conventional techniques still encounter many problems and difficulties in implementing these components, especially from an economical point of view.